English

• In recent years, water pollution, notably from pharmaceuticals like tetracycline (TC), have emerged as critical threats to human survival, affecting both aquatic ecosystems and human health [1,2]. Additionally, the combustion of fossil fuels and industrial utilization contributes to air pollution, including NO_x, which has adverse effects on human health and ecological environment [3-5]. Photocatalytic technology offers a promising alternative to conventional methods for addressing water and air pollution due to its cost-effectiveness, utilization of abundant resources, and eco-friendly nature [6,7]. However, current photocatalytic materials encounter issues like limited light absorption, high rates of electron-hole recombination and poor light responsiveness [8]. Moreover, existing photocatalysts are often specialized for either water or air treatment, lacking versatility. Hence, there is a pressing need for a versatile photocatalyst that can efficiently degrade tetracycline in water and purify NO in air [9,10].

  Bi₂WO₆ stands out among appealing candidate semiconductors due to its appropriate band gap of approximately 2.7 eV and desirable photostability. However, the original Bi₂WO₆ exhibits deficiencies in light absorption and electron-hole separation, impeding its practical application [11,12]. Overcoming these challenges involves incorporating surface oxygen vacancies, which offer significant advantages by modifying the electronic structure and optical properties of the photocatalyst. This activation of the oxygen-deficient surface creates an electron-rich center, potentially lowering the band gaps of semiconductors and enhancing their responsiveness to visible light [13]. Additionally, the formation of heterojunction between Bi₂WO₆ and a compatible semiconductor demonstrates promising application potential.

  TiO₂, as a widely researched semiconductor photocatalyst, has gained considerable interest in photocatalysis for environmental remediation. Its photocatalytic effectiveness largely reliant on the efficient separation of photogenerated electron-hole pairs. Ti₃C₂, with its 2D layered structure and unique distribution of Ti and C components, acts as an excellent precursor for synthesizing TiO₂@C hybrid materials [14,15]. The 2D layered carbon can accelerate electron transport and stabilize TiO₂, leading to improved photocatalytic performance [16,17]. Therefore, Ti₃C₂-derived TiO₂@C holds potential as a material that can improve electron-hole separation and enhance photocatalytic efficiency when forming heterojunctions with Bi₂WO₆ [18,19]. Among various heterojunctions, the S-scheme heterojunction, which creates an internal electric field (IEF), stands out as it accelerates the recombination of ineffective electrons and holes, which can greatly preserve the charge carriers that play an effective role in the photocatalytic reaction, so as to promote the photocatalytic performance [20]. Furthermore, the high Fermi energy level and conduction band position of Bi₂WO₆ provide the feasibility for its formation of an S-scheme heterojunction with TiO₂ [21].

  Based on these findings, Ti₃C₂-derived TiO₂@C was securely attached to Bi₂WO₆ with oxygen vacancies (BWO) to successfully fabricate the S-scheme heterojunction, enhancing the photocatalytic activity for the degradation of TC and removal of NO. Initially, Ti₃AlC₂ was treated with HF to eliminate the Al layer. Subsequently, Ti₃C₂ MXene was produced through layering with DMSO, and TiO₂@C was synthesized via calcination at 500 ℃, guided by the Thermal gravimetric analyzer (TG) and Derivative thermogravimetric (DTG) curves in Fig. S1 (Supporting information). In this study, BWO was synthesized via a hydrothermal method employing ethanol and ethylene glycol as solvents. Simultaneously, TiO₂@C was incorporated during synthesis to create the BWO/TiO₂@C composite (Scheme 1), in which the layered carbon facilitated the separation and transportation of charge carriers. The optimal photocatalyst possessed a TC degradation rate of 84.03% and NO removal rate of 44.2%. The utilization of Ti₃C₂-derived TiO₂@C holds promising prospects as it expands the absorption spectrum to include visible light and facilitates efficient separation of photogenerated charge carriers, thereby enhancing the catalytic performance in photocatalysis.

  Scheme 1

  

  Scheme 1.  Schematic diagram of the BWO/TiO₂@C photocatalysts fabrication process.

  DownLoad: Full-Size Img PowerPoint

  First, the successful synthesis of TiO₂@C was demonstrated by X-ray diffraction (XRD) and Raman spectroscopy (Figs. S2 and S3 in Supporting information), followed by the formation of a heterojunction with BWO. Fig. 1a showed the XRD of Bi₂WO₆, BWO and BWO/TiO₂@C-X. The peaks observed at 28.4°, 32.82°, 46.98° and 55.88° correspond to the (113), (200), (206) and (313) crystal planes of Bi₂WO₆ (JCPDS No 73–2020), respectively. Notably, no peaks corresponding to TiO₂@C were observed, possibly due to the low amount of TiO₂@C added. In addition, in the enlarged XRD spectra ranging from 27° to 30°, the (113) peaks of BWO and BWO/TiO₂@C-X had higher angular displacements compared to Bi₂WO₆, which possibly due to the presence of oxygen vacancies or TiO₂@C [21].

  Figure 1

  

  Figure 1.  (a) XRD patterns of Bi₂WO₆, BWO, and BWO/TiO₂@C-X. (b) FT-IR spectra of Bi₂WO₆, BWO, BWO/TiO₂@C-10 and TiO₂@C. (c, d) TEM and HRTEM images of BWO/TiO₂@C-10.

  DownLoad: Full-Size Img PowerPoint

  Next, the Fourier transform infrared spectrometer (FT-IR spectra) of Bi₂WO₆, BWO, BWO/TiO₂@C-10 and TiO₂@C were shown in Fig. 1b. TiO₂@C exhibited a distinct broadband signal in the 400–900 cm⁻¹ range, attributed to Ti-O-Ti interactions [22,23]. A peak corresponding to the stretching vibration of the hydroxyl (-OH) group was detected at approximately 3400 cm⁻¹. Furthermore, at around 1580 cm⁻¹, a prominent peak representing the stretching vibration of C=C bonds was detected, signifying the successful formation of layered carbon structures [16,24]. Vibrations associated with W-O, Bi-O, and W-O-W bonds were observed at 546, 730, and 1392 cm⁻¹ [21], respectively, with increased absorption intensities after the introduction of oxygen vacancies.

  Then, the morphological characteristics of the photocatalysts were elucidated using scanning electron microscope (SEM). Bi₂WO₆ and BWO were similar in morphology, with Bi₂WO₆ appearing as an irregular flower bulb shape (Fig. S5a in Supporting information). In contrast, BWO had a more regular morphology characterized by uniform three-dimensional flower-like folds (Fig. S5b in Supporting information). The BWO/TiO₂@C-10 (Fig. S5c in Supporting information) maintained the ultra-thin nanosheet structure akin to the BWO. Furthermore, the enlarged view of BWO/TiO₂@C-10 revealed that some TiO₂@C particles was loaded on the surface of BWO (Fig. S5d in Supporting information). To validate the elemental distribution in the BWO/TiO₂@C-10, element mapping analysis was conducted (Fig. S5e in Supporting information), demonstrating the uniform presence of Bi, O, W, Ti and C elements. Figs. 1c and d and Figs. S5f and g (Supporting information) presented the morphological characteristics of BWO/TiO₂@C-10 by employing transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM). Fig. S5f exhibited distinct ultrathin nanosheets with a transparent appearance, in accordance with the SEM. The corresponding magnified images (Fig. 1c and Fig. S5g) revealed the successful formation of a composite with TiO₂ particles on the surface of Bi₂WO₆. Meanwhile, the HRTEM image (Fig. 1d) revealed distinct lattice fringes of 0.345 nm, corresponding to the (101) planes of anatase phase TiO₂ [25], and a lattice spacing of 0.324 nm was determined, corresponding to the (315) crystal plane of Bi₂WO₆, validating the successful synthesis of BWO/TiO₂@C-10.

  Electron paramagnetic resonance (EPR) analysis was performed to illustrate the presence of oxygen vacancies and investigate the influence of solvents on their creation. Fig. 2a showed that while TiO₂@C and Bi₂WO₆ displayed a faint EPR signal, BWO and BWO/TiO₂@C-10 exhibited a stronger EPR signal at g = 2.005, indicating the characteristic of the electrons trapped in oxygen vacancies [26]. Significantly, the EPR signal notably increased from BWO to BWO/TiO₂@C-10, indicating that the inclusion of TiO₂@C in the synthesis process might lead to the formation of additional oxygen vacancies in BWO. To investigate the surface chemical composition and electron state of photocatalysts, X-ray photoelectron spectroscopy (XPS) was conducted. The O 1s spectrum of Bi₂WO₆ (Fig. 2b) displayed three peaks, corresponding to lattice oxygen atoms in the Bi-O and W-O forms, and surface-adsorbed oxygen species (-OH, H₂O, etc.), respectively. Typically, surface oxygen vacancies tend to adsorb more oxygen species, leading to an increase in peak intensity at approximately 532 eV [21], which could elucidate the enhancement in the peak area around 532 eV for BWO and BWO/TiO₂@C-10 in comparison to Bi₂WO₆. In Fig. 2c, no distinct variations were observed in the XPS spectra of Bi 4f peaks in Bi₂WO₆ and BWO, with the peaks at 159.15 and 164.46 eV corresponding Bi 4f_7/2 and Bi 4f_5/2, respectively [27]. Conversely, the Bi 4f binding energy position in BWO/TiO₂@C-10 exhibited a slight shift, suggesting surface charge transfer from BWO to TiO₂@C [28]. The W 4f spectra of Bi₂WO₆ (Fig. S6b in Supporting information) displayed two main peaks at 37.25 and 35.09 eV, corresponding to W 4f_7/2 and W 4f_5/2, respectively. The binding energies of W 4f in BWO and BWO/TiO₂@C-10 showed a slight left shift compared to Bi₂WO₆, primarily attributed to the creation of oxygen vacancies [29]. Simultaneously, the change in binding energy between BWO (37.47 and 35.35 eV) and BWO/TiO₂@C-10 (37.61 and 35.48 eV) may be linked to the transfer of electrons from BWO to TiO₂@C. The C 1s XPS spectrum of BWO/TiO₂@C-10 exhibited a peak at 284.80 eV, corresponding to C═C bonds (Fig. S6c in Supporting information). Furthermore, the oxygen species absorbed onto the layered carbon exhibited peaks at 286.48 eV (C—O) and 288.36 eV (Ti-O-C), respectively [30,31].

  Figure 2

  

  Figure 2.  (a) EPR spectra of Bi₂WO₆, TiO₂@C, BWO and BWO/TiO₂@C-10. (b) O 1s, and (c) Bi 4f XPS spectra of Bi₂WO₆, BWO and BWO/TiO₂@C-10.

  DownLoad: Full-Size Img PowerPoint

  To assess the light absorption performance and energy band structure of the samples, we employed ultraviolet–visible spectroscopy (UV–vis spectroscopy). In Fig. S8a (Supporting information), the light absorption capability and absorption area of BWO and BWO/TiO₂@C-X were enhanced, which can be attributed to the introduction of oxygen vacancies. BWO and BWO/TiO₂@C-X exhibited a certain redshift in their light absorption band edges (around ~470 nm), indicating a broader range of visible light absorption. The band gaps for Bi₂WO₆, BWO and TiO₂@C were assessed to be 2.84, 2.74, and 2.91 eV using Tauc plots (Fig. S8b in Supporting information). Detailed bandgap structures were shown in Figs. S8c-f (Supporting information). Furthermore, the photoluminescence spectrum (PL), photocurrent response, and electrochemical impedance spectroscopy (EIS) analyses (Fig. S9 in Supporting information) collectively validated the augmented photochemical characteristics of BWO/TiO₂@C-10.

  The photocatalytic activity of the as-prepared samples was assessed through TC degradation and NO removal. The dark adsorption rates for Bi₂WO₆, BWO, BWO/TiO₂@C-5, BWO/TiO₂@C-10 and BWO/TiO₂@C-20 in TC degradation were 7.86%, 14.76%, 14.80%, 22.58% and 16.23%, respectively (Fig. 3a), correlating with the specific surface area and pore size analysis (Fig. S10 in Supporting information). After 2 h illumination, the removal rates were 54.72%, 65.14%, 65.14%, 84.03% and 70.01%, respectively. The slight decrease in the photocatalytic activity of BWO/TiO₂@C-20 may be attributed to an excess of TiO₂@C leading to a reduction in the number of exposed active sites. The rate constant (k) for TC degradation was further calculated with the quasi-first-order kinetic equation, as shown in Fig. 3b and Table S2 (Supporting information), with BWO/TiO₂@C-10 exhibiting the highest rate constant. This enhancement could be attributed to the heightened ability to absorb visible light resulting from the incorporation of oxygen vacancies and the improved charge carrier separation and transfer in the interaction between BWO and TiO₂@C. In addition, TiO₂@C was replaced with TiO₂ nanoparticles (P25) to synthesize BWO/P25–10. Results in Fig. S11 (Supporting information) showed that BWO/TiO₂@C-10 outperformed BWO/P25–10, highlighting the crucial role of the carbon layer in photocatalytic reaction. Stability tests were conducted for BWO/TiO₂@C-10 through cyclic photocatalytic degradation experiments (Fig. S12a in Supporting information), confirming the exceptional photocatalytic performance and stability of BWO/TiO₂@C-10 even after prolonged use. XRD analysis further corroborated the stability of the material (Fig. S12c in Supporting information). Furthermore, investigations were conducted on the influence of catalyst dosage, initial TC concentration, initial pH, varying concentrations of inorganic cations (Na⁺, Mg²⁺, K⁺ and Ca²⁺), and inorganic anions (Cl⁻, SO₄²⁻, CO₃²⁻ and HCO₃⁻) on TC elimination by BWO/TiO₂@C-10 (Figs. S13-S15 in Supporting information).

  Figure 3

  

  Figure 3.  Degradation performance of TC (a), rate constant (b), photocatalytic activity of NO removal (c) by Bi₂WO₆, BWO and BWO/TiO₂@C-X.

  DownLoad: Full-Size Img PowerPoint

  After 30 min visible light irradiation, the NO removal rates for Bi₂WO₆, BWO, BWO/TiO₂@C-5, BWO/TiO₂@C-10, and BWO/TiO₂@C-20 were recorded at 9.22%, 29.68%, 30.89%, 44.18%, and 33.56% (Fig. 3c) and the NO₂ concentration was consistently maintained at a low level (<15 ppb) (Fig. S16 in Supporting information). Notably, among these samples, BWO/TiO₂@C-10 exhibited a remarkable 34.96% enhancement in NO removal efficiency compared to the original Bi₂WO₆, showcasing superior performance. Moreover, it demonstrated satisfactory stability throughout the 4-cycle experiment (Fig. S12b in Supporting information) and the XRD results further validated its stability (Fig. S12c in Supporting information).

  Liquid chromatograph mass spectrometry (LC-MS) experiments were conducted to identify potential intermediates generated during the photocatalytic process and elucidate the degradation pathway of TC by BWO/TiO₂@C-10, as demonstrated in Fig. S17 (Supporting information), Table S3 and Scheme S1 (Supporting information). Initially, TC was oxidized by reactive oxygen species such as ^•OH and ^•O₂⁻, resulting in the formation of intermediate products P1, P2, P3, …, P12, then undergoing further oxidation and decomposition, eventually leading to complete mineralization into CO₂, H₂O, and NH₄⁺. By utilizing in-situ DRIFTS to monitor the intermediate and final products during the photocatalytic oxidation of NO (Fig. S18 and Table S4 in Supporting information), it aided in inferring the reaction pathway for NO oxidation, as illustrated in Scheme S2 (Supporting information). When original Bi₂WO₆ was used for NO oxidation, its capability was insufficient to achieve complete deep oxidation of NO, inevitably leading to the generation of toxic gases such as NO₂ during the oxidation process. In contrast, the infrared spectrum of BWO/TiO₂@C-10 revealed an increased number of peaks corresponding to NO₃⁻, suggesting that the modified sample was more proficient in achieving deep oxidation of NO. For more detailed analysis of the pathways for TC removal and NO oxidation, please refer to the supporting information.

  Density functional theory (DFT) calculations (Fig. 4 and Fig. S19 in Supporting information) demonstrated that the formation of a heterojunction between BWO and TiO₂ resulted in the spontaneous transfer of electrons from BWO to TiO₂, generating an internal electric field (IEF). This phenomenon facilitated the recombination of ineffective charge carriers, improved the separation and transfer efficiency of effective charge carriers, and maintained the high oxidation and reduction capacities of the materials. This characteristic aligns with the S-scheme heterojunction, as further evidenced by reactive species testing (Figs. S20 and S21 in Supporting information). Furthermore, through free radical trapping experiments (Figs. S20a and b), it was collectively confirmed that ^•O₂⁻ acted as the primary active species in the photocatalytic process.

  Figure 4

  

  Figure 4.  Work function of (a) BWO, (b) TiO₂ and (c) planar-average charge density of BWO/TiO₂.

  DownLoad: Full-Size Img PowerPoint

  Based on the aforementioned analysis, we put forward a plausible S-scheme heterojunction photocatalytic mechanism of the BWO/TiO₂@C, as shown in Figs. S20e and S22 (Supporting information). Upon the formation of a heterojunction between BWO and TiO₂, significant interactions could arise involving the Bi-O bonds (W originating from BWO and O from TiO₂). Due to the higher Fermi level of BWO compared to TiO₂, electrons spontaneously migrated from BWO to TiO₂, causing energy band bending and resulting in the generation of IEF. BWO and TiO₂ were excited under visible light, producing photoinduced electron-hole pairs. Driven by the IEF, electrons from the conduction band (CB) of TiO₂ moved towards the valence band (VB) of BWO, with the carbon layer aiding in electron transfer, thereby expediting the recombination of electrons in TiO₂ and holes in BWO. Consequently, the holes in TiO₂ and the electrons in BWO remained on their respective surfaces, participating in further photocatalytic reactions. Specifically, electrons in BWO reacted with O₂ to yield ^•O₂⁻, while holes in TiO₂ interact with OH⁻ to generate ^•OH. The S-scheme heterojunction maximized the retention of the high oxidation ability of the VB of TiO₂ and the high reduction ability of the CB of BWO, resulting in the generation of more reactive oxygen species. Consequently, the BWO/TiO₂@C-10 demonstrated exceptional efficacy in the photocatalytic degradation of tetracycline into carbon dioxide and water, along with the oxidation of NO into nitrates or nitrites.

  In summary, TiO₂@C, derived from calcined Ti₃C₂ nanosheets, was incorporated into the BWO hydrothermal synthesis process to obtain BWO/TiO₂@C S-scheme bifunctional catalysts for degrading organic pollutants and purifying NO. Experimental results indicated that BWO/TiO₂@C-10 achieved a degradation efficiency as high as 84.03% for TC and the NO removal rate reached 44.2%. DFT calculations and reactive species testing results confirmed that the heterojunction between BWO and TiO₂@C was conducive to the generation of crucial active radicals. The degradation pathway and intermediate products of TC were determined through LC-MS, and the oxidation pathway of NO to nitrate was further investigated through in-situ DRIFTS. Ti₃C₂ MXene was calcined to oxidize Ti for obtaining TiO₂@C, which was then integrated with BWO featuring oxygen vacancies to promote the separation of charge carriers. Additionally, layered carbon further aided in electron transfer, thereby improving the overall photocatalytic performance.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  CRediT authorship contribution statement

  Xingyan Liu: Writing – original draft, Visualization, Validation, Methodology, Investigation, Formal analysis. Kaili Wu: Writing – original draft, Visualization, Validation, Methodology, Investigation, Formal analysis. Yacen Tang: Writing – original draft, Visualization, Validation, Methodology, Investigation, Formal analysis. Ning Qi: Writing – original draft, Supervision, Project administration, Formal analysis, Conceptualization. Yumeng Zhang: Investigation, Formal analysis. Youzhou He: Writing – original draft, Supervision, Project administration, Conceptualization. Min Fu: Formal analysis. Yanhui Ao: Writing – original draft, Supervision, Project administration, Conceptualization.

  Acknowledgments

  This work was supported by the National Natural Science Foundation of China (Nos. 22001026 and 52100179), the Natural Science Foundation Project of Chongqing (Nos. CSTB2024NSCQ-LZX0073 and CSTB2022NSCQ-MSX1308), the Chongqing College Students' Innovation and Entrepreneurship Training Program (No. S202311799025), and the Science and Technology Research Program of Chongqing Municipal Education Commission (Nos. KJZD-K202300806, KJQN202200821, KJQN202400810, and KJQN202100831). We also would like to thank the Shiyanjia Lab (www.shiyanjia.com) for XPS test.

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2025.110882.

  
  
• 1. [1]

     F. Wang, Y. Gao, H. Fu, et al., Appl. Catal. B: Environ. 339 (2023) 123178. doi: 10.1016/j.apcatb.2023.123178

  2. [2]

     T. Wang, C. Zhao, L. Meng, et al., Appl. Catal. B: Environ. 334 (2023) 122832. doi: 10.1016/j.apcatb.2023.122832

  3. [3]

     S. Wang, W. Cui, B. Lei, et al., Environ. Sci. Technol. 57 (2023) 12890–12900. doi: 10.1021/acs.est.3c03396

  4. [4]

     M. Xu, P. Zhu, Q. Cai, et al., Chin. Chem. Lett. 35 (2024) 109524. doi: 10.1016/j.cclet.2024.109524

  5. [5]

     Y. Huang, S. Liu, M.M. Pei, et al., Rare Metals 42 (2023) 3755–3765. doi: 10.1007/s12598-023-02369-y

  6. [6]

     G. Jiang, X. Liu, H. Jian, et al., Chin. Chem. Lett. 33 (2022) 3049–3052. doi: 10.1016/j.cclet.2021.09.047

  7. [7]

     Y. Shi, Z. Yang, L. Shi, et al., Environ. Sci. Technol. 56 (2022) 14478–14486. doi: 10.1021/acs.est.2c03769

  8. [8]

     X. Liu, C. Jia, G. Jiang, et al., Chin. Chem. Lett. 35 (2024) 109455. doi: 10.1016/j.cclet.2023.109455

  9. [9]

     Q. Zhang, L. Jiang, J. Wang, et al., Appl. Catal. B: Environ. 277 (2020) 119122. doi: 10.1016/j.apcatb.2020.119122

  10. [10]

      Q. Zhang, T. Wu, H. Che, et al., Surf. Interfaces 47 (2024) 104205. doi: 10.1016/j.surfin.2024.104205

  11. [11]

      Z. He, M.S. Siddique, H. Yang, et al., J. Cleaner Prod. 339 (2022) 130634. doi: 10.1016/j.jclepro.2022.130634

  12. [12]

      Y. Wu, P. Wang, H. Che, et al., Angew. Chem. Int. Ed. 63 (2024) e202316410. doi: 10.1002/anie.202316410

  13. [13]

      T. Chen, L. Liu, C. Hu, et al., Chin. J. Catal. 42 (2021) 1413–1438. doi: 10.1016/S1872-2067(20)63769-X

  14. [14]

      X. Kong, P. Gao, R. Jiang, et al., Appl Catal A: Gen. 590 (2020) 117341. doi: 10.1016/j.apcata.2019.117341

  15. [15]

      M. Han, X. Yin, X. Li, et al., ACS Appl. Mater. Interfaces 9 (2017) 20038–20045. doi: 10.1021/acsami.7b04602

  16. [16]

      Z. Wu, Y. Liang, X. Yuan, et al., Chem. Eng. J. 394 (2020) 124921. doi: 10.1016/j.cej.2020.124921

  17. [17]

      H. Che, X. Gao, J. Chen, et al., Angew. Chem. Int. Ed. 60 (2021) 25546–25550. doi: 10.1002/anie.202111769

  18. [18]

      J. Low, L. Zhang, T. Tong, et al., J. Catal. 361 (2018) 255–266. doi: 10.1016/j.jcat.2018.03.009

  19. [19]

      W. Liu, P. Wang, Y. Ao, et al., Adv. Mater. 34 (2022) 2202508. doi: 10.1002/adma.202202508

  20. [20]

      Q. Xu, L. Zhang, B. Cheng, et al., Chem 6 (2020) 1543–1559. doi: 10.1016/j.chempr.2020.06.010

  21. [21]

      S. Xiong, S. Bao, W. Wang, et al., Appl. Catal. B: Environ. 305 (2022) 121026. doi: 10.1016/j.apcatb.2021.121026

  22. [22]

      S.F. Hosseini, M.S. Seyed Dorraji, M.H. Rasoulifard, Compos. Part B: Eng. 262 (2023) 110820. doi: 10.1016/j.compositesb.2023.110820

  23. [23]

      T. Ke, S. Shen, K. Yang, et al., Nanotechnology 31 (2020) 345603. doi: 10.1088/1361-6528/ab90ba

  24. [24]

      W. Yuan, L. Cheng, Y. Zhang, et al., Adv. Mater. Interfaces 4 (2017) 1700577. doi: 10.1002/admi.201700577

  25. [25]

      X. Han, L. An, Y. Hu, et al., Appl. Catal. B: Environ. 265 (2020) 118539. doi: 10.1016/j.apcatb.2019.118539

  26. [26]

      H. Yu, J. Li, Y. Zhang, et al., Angew. Chem. Int. Ed. 58 (2019) 3880–3884. doi: 10.1002/anie.201813967

  27. [27]

      R. Tao, X. Li, X. Li, et al., J. Colloid Interface Sci. 572 (2020) 257–268. doi: 10.1016/j.jcis.2020.03.096

  28. [28]

      X. Ren, K. Wu, Z. Qin, et al., J. Alloys Compd. 788 (2019) 102–109. doi: 10.1016/j.jallcom.2019.02.211

  29. [29]

      S. Zhang, W. Pu, A. Chen, et al., J. Hazard. Mater. 384 (2020) 121478. doi: 10.1016/j.jhazmat.2019.121478

  30. [30]

      J. Wang, Y. Shen, S. Liu, et al., Appl. Catal. B: Environ. 270 (2020) 118885. doi: 10.1016/j.apcatb.2020.118885

  31. [31]

      X. Kong, Z. Peng, R. Jiang, et al., ACS Appl. Nano Mater. 3 (2020) 1373–1381. doi: 10.1021/acsanm.9b02217

• 

  Scheme 1  Schematic diagram of the BWO/TiO₂@C photocatalysts fabrication process.

  下载: 全尺寸图片 幻灯片
  

  Figure 1  (a) XRD patterns of Bi₂WO₆, BWO, and BWO/TiO₂@C-X. (b) FT-IR spectra of Bi₂WO₆, BWO, BWO/TiO₂@C-10 and TiO₂@C. (c, d) TEM and HRTEM images of BWO/TiO₂@C-10.

  下载: 全尺寸图片 幻灯片
  

  Figure 2  (a) EPR spectra of Bi₂WO₆, TiO₂@C, BWO and BWO/TiO₂@C-10. (b) O 1s, and (c) Bi 4f XPS spectra of Bi₂WO₆, BWO and BWO/TiO₂@C-10.

  下载: 全尺寸图片 幻灯片
  

  Figure 3  Degradation performance of TC (a), rate constant (b), photocatalytic activity of NO removal (c) by Bi₂WO₆, BWO and BWO/TiO₂@C-X.

  下载: 全尺寸图片 幻灯片
  

  Figure 4  Work function of (a) BWO, (b) TiO₂ and (c) planar-average charge density of BWO/TiO₂.

  下载: 全尺寸图片 幻灯片
•